


Bruce Abbot's test data is now included on www.flybrushless.com
Thanks again Bruce for allowing me to add it to the site. Enjoy, Robert 




Robert
A possible enhancement to the tabulated data in Flybrushless. If efflux velocity was included allong with each static thrust value, then the power injected into the slipstream by the prop [SS power] could be evaluated. This power, divided by the battery output power would give the overall efficiency of the motor+prop combination. Strictly speaking, this power value [SS power] is correct only for the static case [zero flying speed], as for all the other static measurements. With experience factored in, just two numbers [SS power and efflux velocity], would be a sufficient description of a power train to match it to a model. 



How do you measure efflux velocity accurately  I've tried the Eagle Tree pitot tube airspeed indicator, but the results are nowhere near consistent  I can't determine exactly where to place the tube to get accurate results (both in terms of distance from the hub in relation to prop diameter, and how far behind the prop). I've also tried a Kestrel, but again, where do you place it (without it seriously interfering with the air flow).




Sorry but I'm not familiar with the the efflux velocity (I will look it up later), but is this something that has to be measured or can it be calculated from the existing data?
I'm always looking for ways to improve the site. I have considered adding a calculation to predict the current/rpm for a given prop/voltage. Similar to what Drive Calculator does, but at lot simpler (and most likely less accurate). However I'm not sure if this is a road I should go down since others are doing it. Robert 



Robert  it has to be measured  I don't understand all the intricacies, but I think, basically, it gives you a way of comparing the air speed off the prop (and from equations, the amount of power "injected into the slipstream") with the calculated pitch speed at a certain rpm.




Interesting thing happened this morning.
I went to the Web site and tried a list of motors that I've created for something, probably about 30 outrunners in all in the 143g to 170g weight range, and not one of them had data on the site. Seems to me that all the motors with data entries are tiny. Just an observation. 



Ken,
I did a search on my site and there are only 7 motors on my site that have weights between 143170 grams. http://www.flybrushless.com/search/a...weight/143:170 Of those the only one with any prop data is GPS C3548B I can only show the data I have, and so far I only have test data from Phil (Dr Kiwi) and Bruce Abbot. I think I also have a few results from MicroDan. I am working on a way to share data with Drive Calculator and PeakEff.com. In the mean time if you have any data you would like to add to the site please feel free to. If you already have a lot of test data stored in an excel file, database, etc send me a PM and I can import it for you. That's what I did for Phil's data. Thanks, Robert 



Also none of the Neu motors have any test data for them. I just pulled all of the ones with kv,rm, and io off of their site.
I will get around to adding others later, but for now I'm spending more of my time working on the site rather then adding motors. Robert 



Dr K
I produced the attached plot using a HUGER wind meter. As you see, the velocity varies from point to point. A reasonable average value to record would be 95% of the highest value that can be found. Best if the prop is tested in "pusher" config, with no centrebody to confuse things. The presence of the meter should have zero effect on the upstream flow [ie, upstream of the meter]. 



Quote:
You obviously have a different vision for "tiny" motors... "Tiny" to me is <10g, small is up to 30g, medium is in the 5070g range  I think of anything over 100g as really big! 




Here is a verycompact way to present a large ammount of propeller data from static tests.
For any prop listed, just four numbers provide.... static thrust.... efflux speed......efflux power..... and shaft power .......at any rpm. C/B is the efficiency of the prop acting as a static fan. 



Now all we need is a complete list of props, each with all four constants given!
I can measure Static Thrust and Shaft Power (is that simply Powerin?), and thus get A and B, but I can't measure Efflux Power or Efflux Speed... so C and D are beyond me. 



Hi
Some comments a) Thrust versus (rpm/1000) exponent could be around 2.05 .. 2.10 for a better regression b) Same versus Power in, possible exponent 3.05 .. 3.10 c) Power shaft = Power In  iron losses  copper losses  ESC losses Louis 
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